


This Has Already Happened

by Mollyamory (Molly), Speranza



Category: Marvel Cinematic Universe, The Avengers (Marvel Movies)
Genre: All will be explained, Avengers: Endgame (Movie) Spoilers, M/M, Science Bros, Tony is happy, also did we mention that Steve has a time machine?, but seriously: everybody dies, canonical AU, it's the end of the world as we know it, oh and yes the story runs backwards, rocks fall everybody dies, so you know that things are really terrible
Language: English
Status: Completed
Published: 2019-07-04
Updated: 2019-07-04
Packaged: 2020-06-03 15:09:38
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 7,992
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19466551
Author URL: https://archiveofourown.org/users/Molly/pseuds/Mollyamory, https://archiveofourown.org/users/Speranza/pseuds/Speranza
Summary: "There are absolutely no circumstances in which I give the Time Stone to you," the Wizard gasps. "None. Nada. Zip.  Choke on that, you sonofabitch."





	This Has Already Happened

**Author's Note:**

  * Translation into 中文 available: [This Has Already Happened/覆水难收](https://archiveofourown.org/works/20188588) by [Oxycontin](https://archiveofourown.org/users/Oxycontin/pseuds/Oxycontin)



###  2388 

In the stillness and dust, there is a sudden, loud crack. A huge glass chunk of the Tillman Building falls nineteen stories onto Boylston Street below. The place where it crashes is thick with green shrubs; weeds have grown through the cracks in the pavement, gardens grow out of the sewers. Boston's bridges have long ago sagged and fallen into the Charles. The bronze statue of Sam Adams, greening and weathered, stands lonely behind the ruin of Faneuil Hall. 

Stark Tower looms over all of downtown Boston. The low brick buildings built during the Revolutionary War stand firm, but most of architectural modernity is in shambles. Empty windows hang from the twisted frames of office blocks. The top half of the Hyatt Regency fell over and sank into Boston Harbor sometime in 2306. 

But Stark Tower still stands. It stands because it had been designed and built by MIT MechE professor A.E. Carbonell as a memorial to his father after the Battle of New York. Stark Tower was Carbonell's last project, his masterwork, and his involvement in the building stretched from blueprint to red carpet. It included the development of a proprietary formula for concrete, an elaborate system of wind dampeners, and an environmentally green heating and cooling system. Like the pyramids, Stark Tower was designed to last. 

And so it does, even as the world crumbles around it. Its rooms and halls are empty, but the lights still come on at sunset, every day. The air circulates, cool in summer, warm in winter’s chill. Stark Tower stands, waiting, listening for a voice that will never come. It stands in silence for the most part, but sometimes Jarvis hums sad songs to himself, powered by a tiny arc reactor with a lifespan of 10,000 years. 

  
  


###  2028 

Thanos takes a moment to contemplate the imminent end of the anthropocene. He will soon move to destroy the rest of them, and this pitiful resistance they'd managed to muster. They'd spent nearly a decade struggling to build their primitive time-machine, but it had only been a doorway to their own destruction. Now his armies are pouring through: Chitauri, Kree, Outriders. To face—well, who, exactly? 

The man they call Cap struggles, bleeding, to his hands and knees. He's alone now, the last of Earth's champions. His chest heaves. It looks like it hurts him to breathe. One could almost admire him— _almost,_ because courage is one thing, but this is pure stubbornness. His hands shake as he tightens the strap on his shield, now just a jagged shard of metal. There are tracks running through the dark layer of grime on his face: sweat or tears, maybe. Both, maybe. 

Cap charges, broken shield at the ready, and he's faster than Thanos anticipated, considering the near-certainty of broken bones and internal bleeding. Still, Thanos seizes him, stopping him—but when you stare into the void, the void stares back, and for a long, terrible moment he isn't sure if he has the Captain or the Captain has him. There's a power surging through the man's puny frame that Thanos doesn't understand, a blue lightning, and for a second he feels fear. The Captain has _got_ him: Thanos will burn in the purifying _fire_ of him. But no; no, he won't. 

With a grunt, Thanos snaps the man's neck, holding on til the energy dissipates and he's holding only a ragdoll corpse. All gone now; yes. All gone. Only flesh, now. Only bone. 

Thanos lets the corpse drop and lifts his gauntleted arm. The gems sparkle. "I am inevitable," he explains, almost apologetically—and then he snaps his fingers and all human life ends. 

  
  


###  2020 

When she opens the door, Natasha is both surprised and not the slightest bit surprised to see Steve Rogers standing there, alone. She hugs him, ignoring the tears silently streaming down both their faces. They're past petty vanities now. His arms wrap tight around her, and he's strong, solid. "You came back," she says. 

"Yeah," Steve says, his voice scraping wetly out of his chest. "I came to—work," he grits out, like every word costs him. It probably does. 

"Well, there's work here," Natasha says, in the understatement of the goddamned century. 

Steve pulls back and gives her a hard, serious look. "Natasha, we have to build a time machine," he says, and for a moment, Natasha's gripped by a wild panic, because she needs _Steve of all people_ to have _kept his marbles_ , because _God knows_ she's _on_ _the verge_ of _losing hers_. But then she looks at his face and realizes he's not crazy. He's solid and sensible. He's Steve. 

"A—time machine?" Natasha manages, like it's a reasonable thing for them to be talking about. 

"Yeah," Steve says, and then he sighs and pinches the bridge of his nose. "I know how it sounds, but it's _possible,_ Natasha—Bucky said it was possible, told me he knew it for a goddamned fact, so you can take that to the bank. We just…" Steve's laughter would sound crazy if it weren't the sanest response to this situation. "We just have to figure out how." 

"Well, okay," Natasha says, wiping her eyes. "In the meantime, I'm making spaghetti. Would you like some spaghetti?" 

"I would love some spaghetti," Steve says. 

  
  


###  2019 

The battle goes more easily than Thanos expects. He finds just token resistance: Earth seems weak, pre-defeated. Of course, they have already seen so many wars and invasions, including that of his own Chitauri army several years ago. So they are fighting in the ruins, on land they have already burned. This century, their last, has been one of Pyrrhic victories. 

He only needs one last stone—the Time Stone that the Wizard protects. He grasps the Wizard by the throat. It's true that the curses of the dead are difficult to break, but he has patience, and he will have time on his side. "There are absolutely no circumstances in which I give the Time Stone to you," the Wizard gasps. "None. Nada. Zip. Choke on that, you sonofabitch." 

"You first," Thanos says, and smiles. 

  
  


###  2017 

Bruce Banner isn't big on parties. He hangs out at the periphery, tends to zone out. But after a while even he realizes that Tony's no longer at the center of things. Tony's team is dancing in the atrium of Stark Tower, splashing around the rainwater fountain, clinking champagne glasses that glow pink and purple with the music. But Tony's not there with them. Bruce has a sudden intuition and moves toward the enormous door. From somewhere above him, Jarvis murmurs softly, "Yes. He is on the west side of the building, under the portico." 

"Thanks," Bruce mumbles, and pushes into the cool night air. And there's Tony, walking aimlessly across the piazza, champagne bottle dangling from one hand. He takes a swig, then holds out the green glass bottle to Bruce, offering him a drink. When Bruce waves it away, Tony slides an arm around his neck and kisses him, sloppy, mouth cold and sweet and tasting of champagne. Bruce kisses back, deep and heartfelt: this, he won't turn down. 

"It's amazing, okay?" Bruce says in his most serious voice, because Tony needs to hear it. "Truly amazing. You should be _so_ proud of what you've made here...." 

"I'm proud, I'm proud," Tony says, twitching and restless, and then: "It's not like what you did with nanotech and malaria—" 

"This building's fifty years ahead of its time," Bruce insists. "It's gonna set the standard for decades." 

"It's got my dad's name on it," Tony says, a little despairingly. "In big letters. I caved." 

"But it's got _your heart_ in it, Tony. So you _win,_ okay? You _win,"_ and Bruce tugs him in and hugs him, hard. Tony hugs back, the clutched bottle banging into the small of Bruce's back. 

After a while, Tony pulls back and fixes him with his dark, intelligent eyes. "It wasn't supposed to be this way," he says. "I can't explain how I _know_ that, but I _know_ it, and I think you know it, too." 

Bruce respects Tony more than any man alive, so he gives the idea serious consideration. "Maybe not," he concedes, because New York was a terrible thing, and then there was the pointless stupidity of the Supersoldier Wars, and Tony's father's death. "But in some ways...it's better, right?" Tony's eyebrows fly up: he doesn't seem to have considered that possibility. 

"That's it," Tony exclaims. "I think I'm happy. So somebody screwed up somewhere," and Bruce laughs low, shaking his head. "Come back inside, I'll get them to play some Duran Duran." 

  
  


###  2014 

The hand comes down and pulls Steve up through the debris of the helicarriers, drags him to shore. Steve lays there, heaving, then turns and vomits up water from the Potomac as his vision clears. The smell of burning metal and the greasy feel of the water make his stomach turn. Or maybe it's knowing what S.H.I.E.L.D. has become that's making him sick—this S.H.I.E.L.D that lacks Howard's brain and Peggy's courage. And heart is not enough. Steve claws his hand in the mud and sees a scraggle of green weeds beyond, and the black webbing of Bucky's boot. 

"I _told_ you to wait," Bucky says, shaking his head; he's drenched, too, and he's got bits of leaves and dirt in his hair. "Two more minutes and we could have _landed_ those damn things." 

_"Land_ them? I didn't want to _land_ them." Steve struggles to sit up, spits into the dirt. "I wanted to _blow them out of the goddamn sky_ —I mean, is there anyone in the world that you'd trust to have firepower like that? S.H.I.E.L.D.? The army?" Even the river water stinks of betrayal. 

"Hey, I've never trusted anyone but you, pal," Bucky says with a strange, interior smile. 

"Well, maybe that was a mistake." Steve looks around dispiritedly. "I don't seem to have landed you anywhere good. I don't even know who the hell we're working for anymore…" 

"Yeah, so about that," Bucky says, hunching forward. "I say we make a break for it," and when Steve looks up, shocked, Bucky just nods, waiting for the idea to sink into his thick skull. "Disappear," Bucky confirms. "Go underground. This is our chance, pal—but you're gonna have to follow _my_ lead for a change because stealth is not what anyone would call _your strong suit._ And you've got to make up your mind right now, because in five minutes this place is going to be swarming with cops and S.H.I.E.L.D. agents, some of who are gonna be _HYDRA_ agents, and—" 

"I'd follow you to the ends of the earth," Steve says, and means it with all his heart. 

  
  


###  2012 

In seconds the city is swallowed by blinding light. Steve throws up a hand to protect his eyes, and beside him Maria Hill does something to a screen that darkens all the bridge windows on the helicarrier. The sound reaches them seconds later, a roar that rocks the helicarrier across the sky. Across the deck S.H.I.E.L.D. agents fall to their knees, to their chairs, but all eyes are forward, all eyes are watching New York City burn. It goes up like a Roman candle, a million lives erased, a million stories ended. A sacrifice play—or so they said. No choice, they said. 

The portal closes. One by one, the Chitauri aircraft fall from the sky. Behind him, someone is gasping in great, lung-tearing sobs. This, Steve understands, is what winning looks like in this new, cold world. They've cauterized Manhattan, that tiny, little island between Europe and America, to stop the world from bleeding out. Steve numbly presses his fingertips to the glass; this high up, he can see the long, narrow shape of the city. He and Bucky died once, already, trying to stop the bombs from reaching New York. But they'd only delayed things, it seems. 

Panic, nausea, rises up to choke him—and then Bucky's hand drops on his shoulder, reassuring and warm. "There wasn't anything you could have done, pal," Bucky mutters softly. "There wasn't anything _anyone_ could have done here," and _Christ,_ Steve can only hope that's true. 

  
  


###  2011 

They're not the Howling Commandos, but after a decade heading makeshift teams, it's good to have a group of people he can trust. The dame—woman— _Natasha_ —is the best of them, a fact which is so clear and obvious that Steve's surprised when the brass give him an argument about it. So much for this feminist movement they keep banging on about—from what Steve can see, they've got new and fancy words for everything, but they still can't see the female talent under their goddamned noses. He and Natasha understand each other well enough though, and there's a like-attracted-to-like thing happening that reminds him of the instant connection he felt with Peggy, all those many years ago. Clint Barton is also a first-rate pick—Bucky says because archery is one of those things you just can't do if you're an asshole; archery's an asshole-detector, Bucky says, because you need to be still and calm in yourself. Disciplined. You need to think and act at the same time. You can't be going off half-cocked. 

They also add an airman named Sam Wilson, a Special Forces pararescueman trained on the experimental Exo-7 Falcon flight gear. Like them, Wilson was on the verge of getting out—but extended his tour of duty after discovering that Captain America wanted him for his team. 

Steve feels a bit bad about that. "Don't," Bucky says, and of course he has Bucky beside him; he wouldn't be able to go on without Bucky, he's sure of that. "He's made his bed, like we've made ours. Or wait, maybe it was _you_ that made mine," he says, and then laughs and laughs. 

  
  


###  2002 

Steve and Bucky fight in the Supersoldier Wars even though they don't want to. S.H.I.E.L.D. had sworn up and down that their tour of duty would expire with the century, then filed deferment after deferment. But when the war breaks out in 2002, they join the fight—for Howard Stark, because they owe their lives to Howard Stark, and Howard was the war's first casualty, murdered by Mark Four, a Supersoldier prototype. Nobody even knew that Stark Industries was doing human trials—that is, until Mark Four killed Howard Stark and escaped with the formula. A month later, a strike team of Supersoldiers launched an attack on DC. 

"As far as I'm concerned, the sonovabitch had it coming," Stark's son, Tony Carbonell said; he'd cornered them at Howard's memorial, which he'd attended blind drunk and still carrying a flask. "He just _couldn't let it go_ , those dreams of wartime glory, of being a goddamned hero— but you guys know that, right? You of _all_ people." Tony takes a long, sloppy swig out of the flask as Steve and Bucky exchange loaded glances. "He wasn't ever gonna let you boys rest in peace—and don't delude yourself he was looking for _you_ in that iceberg. He was looking for the _shield_ , he was looking for one of his _inventions_ , his goddamned _property._ So he could arm the next generation of Supersoldiers. _Some. People. Never. Learn._ " 

"Tony, come on," a bespectacled man says gently, tugging at Carbonell's arm. "Don't do this—" 

"Your father was a good man, Tony," Steve said quietly. "It's easy to get caught up in—" 

"What—in war? Competitive national homicide? You tell me. I hear it's a growth industry, killing people. Dad wanted me to take over the family business, the weapons business—" Tony barked out a laugh. "— _as if._ But _I got out_ —and _Mom,_ she got out, too, thank Chthulu and all the lords of darkness. You realize she'd be dead, too, if she'd stayed with that sonovabitch." Tony's eyes find Maria Carbonell across the room, looking elegant in a dark suit. "They'd've killed her too. Howard Stark: Voted Most Likely to Get Himself Killed While Taking Innocent People With Him." 

Tony moves to take another swig, but the bespectacled man slyly intercepts the flask and slides it into his jacket pocket. "Come on, let's get out of here, let's get something to eat," he murmurs. 

"Yeah, okay," Tony says, and then, blinking rapidly, he makes introductions. "This is my partner, Dr. Bruce Banner," he says. "He's got an enormous... _brain,_ okay, let's _say_ brain...which he uses, _get this,_ to _help_ people. Wild, right? Bruce, this is Captain America and Bucky—you know, from history? They punched Nazis and stuff. My dad dug them out of a glacier couple of years back." 

Bruce winces. "Yeah, I— hello," he says awkwardly. "It's an honor to—" 

"It's not an _honor_ ," Tony snorts, "these guys are just _hostages_ to my Dad's fucking _ego_ like _everyone_ _else_ ," at which point, Bruce makes Tony's apologies and drags him out of there and up the block to find food. He's pretty sure that they passed a place that sells schwarma. 

  
  


###  1998 

"So what do you think of the place?" The apartment S.H.I.E.L.D. has given them has an enormous window overlooking the Brooklyn Bridge, and Steve just can't get enough of the view. 

Bucky comes to stand beside him, but only glances out. "I think you'd better look your fill," he tells Steve, "Because I don't think we're gonna be spending a lot of time here, you and me." 

This brings Steve up short. "What?" 

"That guy Fury?" Bucky says darkly. "He's got _plans_ for us." 

Steve's frowning now. "He said June, we'd be de-mobbed in June. Special forces after that. A strike team, reserve duty, he said. Exigent circumstances only, he said." 

_"He said, he said..."_ Bucky chants. "You think the brass is gonna leave weapons lying out in the field? You think there's a day that goes by without 'exigent circumstances?' Cause if you do, pal…" Bucky sweeps an arm out toward the view, "I got a bridge in Brooklyn to sell you." 

"You think they're lying?" Steve asks, frowning. 

"Lying, I don't know," Bucky replies, shrugging. "But ten bucks says that we're working in June, and the June after that and the one after that. They're not going to let us go so easy, Steve." 

Steve's frown deepens. "I don't want to win that bet," he says. "I want us to get out. I want to live in the world— _this_ world, with you." 

"This world, this future where everything's different," Bucky says, a little mockingly, "though I notice that Howard still hasn't got a flying car yet," and then Bucky's reaching out, crooking his fingers through the belt loops on either side of Steve's pants and tugging him close. Steve laughs, his face going hot. "The truth is," Bucky says in a low voice that makes Steve's breath catch, "I don't much care where I am or what I'm doing so long as I'm with you. That's the goddamn truth, Steve," and Bucky's hands move to his face and Steve faintly smells coffee on his breath, feels the rasp of his stubble, before their mouths come together and the sharp urgency of his desire—he's scrabbling, hanging on for dear life—drowns out everything else. 

###  1997 

“Tony, have you seen this?” 

He takes the tablet from Bruce, his eyes more on the way Bruce’s hair falls across his forehead than on the screen. There’s one weird curl that keeps falling away from the rest, and Bruce brushes it back every time it gets close to his eyes. Which is a lot. A little hair gel would take care of that problem, but Bruce seems stubbornly unaware of the existence of styling products. 

It’s driving Tony a little insane. 

“What am I looking at?” he says, peeling his eyes off Bruce for probably not the last time today. 

“Here.” Bruce flicks his fingers against the screen, and the window expands into a hologram filled with— his father. Howard Stark is standing on a slab of ice, a cold and distant sun barely clearing the horizon behind him, his face half in shadow. Even so, there’s an expression of deep joy in his eyes that Tony has never seen, has never even imagined was possible. His chest tightens, air filling his lungs too shallow, too slow. He rubs at his sternum, trying to relieve the invisible pressure building there. 

“He found them. The son of a bitch found them.” He doesn’t even have to look at the other pictures; he knows who they are. _Steven Grant Rogers. James Buchanan Barnes._ Howard Stark’s favorite people in all the world—never mind that they’ve been dead half his life. Or maybe that's a plus where his father is concerned; not a bug, but a feature. 

Bruce nudges his shoulder against Tony's, a warm and easy gesture designed to knock him out of his bad brainspace. It reminds Tony that he’s not alone, and Tony bumps back and keeps his thoughts behind his teeth for once. Bad enough, the bitterness and rage those names have sparked in him since he was a kid—since he was old enough to understand his own place in Howard’s life (which wasn’t even last place; it was just _no_ place, nothing.) Bad enough to have that inside him without spilling it on the floor for Bruce to see. Tony has somehow deluded Bruce into believing that he is a healthy, functional adult and he wants to keep it that way. 

“Well, I guess he can die happy now,” Tony says lightly. “After the heroic state funerals and parades, of course. Christ. Traffic’s going to be a nightmare for a while. Where do you think they’ll stash the bodies? Probably have to build a whole new cemetery. Nothing but the best for America’s mightiest heroes, right?” 

“They’re not dead.” Bruce drops onto the sofa, his legs crossed in a position Tony himself couldn’t mimic in a million years. “He found them alive. We’ve always wondered, right, what the serum could do, what the upper limits might be… but it’s incredible, Tony, beyond anything. I can’t even begin to parse the—” Tony doesn't know what's on his face, but Bruce suddenly hesitates, biting his lip. “Sorry. I realize that’s probably not what— I mean, I know you’re— ” 

“Alive,” Tony says, staring. “Like— _alive?_ What, have they been living in igloos all this time? ‘Gone ice fishing, back in fifty years’? 'See you later, suckers?'” 

“The news is saying they were in the ice, in some kind of cryo-state. They haven’t even aged, apparently. I wonder if that’s to do with the cold, or the serum, or some combination of—” 

Tony rolls his eyes toward the ceiling, affection crowding out his annoyance. So Howard gets his war buddies back, so what? Tony’s got _this._ “Your brain never stops, does it, Banner.” 

Bruce shrugs, a small grin tugging at the corner of his mouth. “My secret super power.” 

“Not so much of a secret after the fifth Ph.D., Doctor. So, what do you think—do I call him? 'Good job, Pop, glad you’ve finally dug up some old friends?' I don't think Hallmark makes a card for that. ‘Happy your secret boyfriends aren’t dead, hope their brains aren't mush?’” 

“I think you can safely skip it.” Bruce shoves his hair back out of his eyes again. “Sorry about your shitty childhood, by the way.” 

Tony catches the spark of humor and starts to grin. “Thank you… for your socially inept attempt at consolation?” 

Bruce laughs. It’s an amazing sound, and it drowns out the last dregs of Tony’s anger. “A friend like you,” Bruce says, “makes normal human interaction a little less terrifying.” 

“A friend, huh?” Tony shakes his head, leaning a little closer. “Is that what we're doing?” 

"I don't know," but Bruce's eyes are glinting behind his glasses, like they do when he sees something interesting. "What do you call it?" 

Tony strokes his chin. "You mean—are you asking my professional opinion, here?" 

"Why, of course," Bruce replies. 

"I'd call it...living the best three years of my life," Tony says, "straight up, no bullshit. You...derail my worst instincts, of which I have—you know, _many._ Many, many. _Mmmmmany."_

Bruce's face is serious now. “You’ve been good for me, too. You get me out of my own head, and that’s—it’s not always a comfortable place to be, so. And at the risk of feeding your ego, you know I think you’re—” 

“Devilishly handsome? Brilliant? Frankly irresistible?” 

“A good man.” Bruce shrugs. “And I’ve known some bad ones, Tony. I know the difference.” 

Tony’s mouth goes dry, his heart kicking up a notch. “Oh yeah?” 

"Mmhm," Bruce says. 

“I’m...really liking the way this conversation is going,” Tony says. Without meaning to, he’s been watching Bruce’s mouth while he talks instead of looking him in the eye; when he corrects that, just to check in, he finds Bruce isn't looking at _his_ eyes, either. 

“And… you are kind of devilishly handsome,” Bruce says, grinning. “But you knew that already.” 

“Well, but I didn’t know _you_ knew it. That’s… that’s kind of amazing. Wow. Does that mean… wait, that’s not like an intellectual assessment, is it? Like, you know it, but do you _appreciate_ it? What level of understanding are we talking about, exactly? Is this appreciation actionable?” 

“Congratulations on your lack of a verbal filter.” Bruce reaches out and fists his hand in Tony’s shirt. He tugs, just a suggestion of effort. “It's reassuring.” The pull gets stronger, and Tony gives into it, leaning in as Bruce falls back against the arm of the sofa. It puts him in Bruce’s arms, and Bruce in his, and that’s exactly what Tony’s been wanting for as long as he can remember. 

Bruce raises his hands to Tony’s face and pulls him even closer. “Wish you were here,” he says, his eyes twinkling, and Tony’s already laughing when their mouths finally come together. 

  
  


###  1994 

“So, I’ve got three problems here.” 

Bruce looks up from his work; it takes a minute to swim up out of the math, and when he finally gets to the surface, he realizes that time has gotten away from him. The world outside the windows of the coffee shop is a lot darker, for one thing. And the guy standing next to his table is not the waitress. He puts his glasses back on to confirm that and oh, yeah, confirmed. 

This guy is _way_ prettier. 

He says, as politely as he can in the face of yet another interruption, “I’m sorry, I didn’t quite catch that. I was _working._ ” 

“Yeah. That’s the first problem. See that guy over there?” The stranger hikes his thumb over his shoulder, where a barista is paying them no attention whatsoever. “His job is to sell food and beverages, and you’re not having any. You want to make him look bad in front of his boss?” 

It’s a fair point. Bruce only came in to get out of the cold, and through the windows he can see that the weather’s only gotten worse—instead of just bitterly cold, it’s now also dark and snowing. Welcome to Boston. “I’ll have a coffee, black,” he says, and when he gets only thinned lips and a flat stare for it, he adds, “and a grilled cheese sandwich?” 

“Thank you. That’s one down. Hey, Tom,” he calls over his shoulder, “can you get this nice gentleman who is now a paying customer a coffee and a grilled cheese?” Tom waves a hand at them, which the guy definitely cannot see because he never takes his eyes off Bruce. 

Bruce frowns. “Shouldn’t you be the one getting my order? You did take it, after all.” 

“I don’t _work_ here,” the guy says, looking mildly horrified. 

__

“Then why—” 

Loftily, he says, “I’m highly invested in this place—I practically lived here when I was an undergrad. It's one hundred and seventy feet from the robotics labs. Give or take. Moving on to my second problem: you’ve been sitting here writing on napkins since three o’clock...” 

Bruce tilts his head. “Since you don’t work here, I’m not entirely sure how that’s your problem.” 

“You ran out of napkins two hours ago.” 

“I —” Bruce looks down at the white tabletop. It’s covered in blue ink, his handwriting filling a wide arc and getting progressively smaller the closer it gets to the edges. His cheeks flush, and he bites his lip, trying to think of an explanation, or an excuse. “I’m sorry,” he says finally, “I don’t usually get so, uh—wow, I have absolutely nothing to say for myself. I’ll clean it off?” 

“Don’t you _dare._ ” The guy pulls out the chair across from Bruce and sits down. “I’m planning to take this tabletop home with me and jerk off to it every night for the rest of my life. You just invented a new element in a coffee shop in the middle of the afternoon and I don’t have any idea who you are. That, in case you’re wondering, is my third problem: Who the hell _are_ you?" 

Bruce loses track of the rapid-fire soliloquy right around “jerk off” and only picks up the thread at the very end. His eyes go wide, and he looks from the tabletop back up to — 

“Who are _you,_ ” he asks wonderingly. “How did you—you can see what this is?” 

“I mean, it’s not really my field. I couldn’t come up with this, I couldn’t _do_ this, but I can follow along well enough.” For a moment the veneer of amusement falls away and his eyes are very, very serious. “I’m kind of in awe here, okay?” 

Bruce knows exactly nobody who could follow along with what he’s done here, and it takes him a second to process that this stranger is … probably not just a waiter. “Who the hell are _you,"_ Bruce says, and just as he finishes saying it, he _knows._

“I’m Tony—” 

“Stark,” Bruce finishes; and of course he is. There’s an entire science building on campus that literally has his name on it, his father’s face in black and white hanging in the lobby. MIT at 14, and the youngest tenure-track hire in the history of the institution. “Dr. Stark, of course." 

“It's Carbonell now, actually,” Tony says firmly, his eyes darkening. “I don’t use that other name anymore." 

“Uh. Sorry.” Bruce shrugs. “I don’t really keep up with the news, so—” 

“It’s okay.” Tony holds out his hand, and Bruce takes it because that’s what you _do,_ only Tony doesn’t let go when the appropriate grip time has passed. “And _you_ are?” he says pointedly. 

“Uh, Bruce Banner.” He takes his hand back—it takes a little more effort than expected—and pushes his hair out of his eyes to get a better look at Tony. He’s definitely a Stark, whatever he calls himself now—that’s the same chin, and those are the same dark eyes Bruce sees on his way to the lab every day. On Tony those eyes don’t look distant or hard, though. On Tony, they just look—interested. Interesting. 

“How do you intend to synthesize it?” Tony asks, his head tilted to see some of the smaller writing on the table. He leans in to trace a line of symbols, and that's close enough that Bruce can smell his cologne, which is unnerving. 

“I—don’t? It’s just theoretical. The technology doesn’t exist yet. Maybe in twenty years or so, but right now it’s just a paper. Maybe a journal article, if I can clean it up some.” Bruce fumbles a notebook out of his backpack and stands up. “Let me copy this down—” 

“Or,” Tony says, pulling a screwdriver from his back pocket, “we can just take it with us.” 

“We?” Bruce steps back as Tony ducks under the table. “Uh… where?” 

“My place.” Tony comes out from under the table with a handful of screws, which he deposits in Bruce’s hand with a wink. He lifts the top of the table off its legs and rests it sideways against his shins. “You should come home with me. I’ve got a _lot_ of cool toys.” 

Bruce’s heart climbs into his throat. “Excuse me?” 

“Not like—don’t look at me like that, I’m not _hitting_ on you, Banner. Though if you were even halfway interested I’d be all over it; you’re completely adorable, and—never mind. Come home with me because I’ve got a workshop you would not _believe,_ equipment at least ten years ahead of anything you’ve ever had access to. Maybe more. Come home with me, and I’ll build you whatever you need. We’ll turn your little journal article into a fucking _Nobel._ ” Tony grins, a wild edge to it. “What do you say?” 

“Okay.” Bruce absolutely believes they can do whatever this guy says. “When?” 

Tony’s smile widens, gets warmer. He claps a hand on Bruce’s shoulder; his fingers are strangely elegant and strong. Bruce peeks at them out of the corner of his eye as Tony calls to the barista, “Hey, Tom? We’re taking this with us. Wrap up that sandwich to go." 

  
  


###  1992 

Howard Stark lets out a noise of dissatisfaction so loud that the waiter at the Union Club assumes he’s out of scotch and scrambles to his side in panic. But Stark's just glaring at his son. "Do you have to take your mother's side in absolutely _everything?_ " he demands. 

It's a stupid question. "Yeah, I do, Dad, _actually._ Because Mom's worth ten of you." 

"Check your math," Howard growls, and waves for the waiter to go away. 

"Hm, carry the four...yeah, you're right. Mom's actually worth 1400 of you, give or take." 

"You're only hurting yourself, you know. If you do it," Howard says. "Stark is a name to conjure with—literally to conjure with. Carbonell?... _pfttt._ " Howard flings a dismissive hand, "What does that mean to anybody? Nothing to nobody," and Tony can't help feeling a mean little twinge of satisfaction: he is gonna hit Howard Stark where he _lives_ — _bam,_ right in the _legacy._

"Actually, I've already done it," Tony says, downing the rest of his scotch. 

Howard stares at him blankly. "You've done what?" and Tony's ready for the moment: he reaches into his jacket and pulls out his wallet, passport, driver's license, credit cards, and thwacks them one at a time down onto the heavy damask tablecloth, _bam, bam, bam._ Anthony Edward Carbonell. A.E. Carbonell. Tony Carbonell. Member since 1984. 

Tony hands his Amex to the waiter with a flourish. He's got cash, but he's been practicing his signature, and he wants to sign it in front of Howard, in big, looping letters: CAR. BON. ELL. 

"Oh, and by the way," Tony says, as he signs, "Great-Grammie Carbonell taught mathematics at Radcliffe, did you know that? That's where she met Great-Grandpa Carbonell. He invented the sound-powered telephone still used in ship to shore communications, as well as a bunch of other staggeringly useful things. Filed for loads and loads of patents, Mom says." 

Howard stares morosely into his drink. "How _is_ your mother?" he asks. 

"She's fine." 

Howard jiggles the ice in his empty glass. "Is she seeing anybody yet?" 

Tony snorts in disgust. "You're a pig." 

Howard doesn't seem to take this personally. "Is she happy to be back with her old friends?" He lets out a bitter laugh. "Living like a Brahmin in Beacon Hill?" 

"Yeah," Tony said. "We both really like living in Boston," and when Howard looked up sharply, Tony said: "Yeah, I'm staying. MIT offered me a job, MechE, accelerated tenure track." 

"I thought you were coming back to work! We're building a new HQ. In midtown. 42nd Street!" 

"Yeah, sorry, not interested," Tony says. 

  
  


###  1991 

The parkway is dark, windy, and overhung with trees, and Howard takes the curves too fast. He's only half-watching the road, because he's fumbling on the seat beside him for his security pass. You have to show a pass to get onto the road that leads to the S.H.I.E.L.D. base in Glen Cove—even _he_ has to show a pass, even though he _founded_ the goddamned place. 

"Howard, please," Maria says, pretending patience, "slow down. I'm not even on the plane yet and I'm experiencing turbulence." 

"Sorry, darling." Howard glances up—and is instantly blinded by a bright flash from his rear view mirror. A moment later he hears the roar of a motorcycle—more than one: two or three. He has the stupid, self-aggrandizing thought that they've sent a motorcade for him and his amazing discovery—before realizing with a snap of cold reason that _no, they've come to kill him._ He reacts instinctively, swerving hard to the left and hitting one of the cycles just as the first shot explodes the Cadillac's rear window. Maria screams, and Howard is all blind instinct, flooring it, ramming the car into a second motorcycle, which has roared up from the other side to cut him off. But if they're expecting him to stop, they're goddamn wrong, and the black-clad figure on the bike only gets off one wild shot before Howard _hits_ him, full force and at top speed, despite the fact that Maria is clawing at his arm and screaming, "Howard! Oh, my God!" The biker flies up and crashes onto the hood of the Cadillac with a satisfying thud before bouncing off and onto the road. Howard doesn't look back, just keeps speeding up the parkway. If there are others, he's going to lose them. He's got to get to S.H.I.E.L.D. 

Beside him, Maria's near-hysterical. "Howard, you _hit_ that man, you've got to stop and—" 

"I'm not stopping," Howard says grimly, and Maria sits back then, gaping and wide-eyed and breathing hard, her hand going instinctively to the string of pearls at her throat. Howard can feel her eyes on him but keeps his eyes fixed on the road. His clutches the wheel tight as he drives. 

"What do those men want?" Maria asks finally. 

"Who the hell knows what they want?" Howard replies, denial as familiar as breathing. 

"Howard, what do they want?" Maria repeats. 

"I've re-synthesized the superserum," Howard says flatly. "Prototype's in the trunk." 

Maria nods slowly and turns to look out her window. 

Half a mile from the S.H.I.E.L.D. guardhouse the real cavalry comes, and he and Maria are swarmed by agents who bustle them and the serum into an armored car and quickly turn the Cadillac and the road into a crime scene. They're swept through the gates and into a secure building, and Howard immediately puts the suitcase of prototype serum into the vault and files a report of the attack with the base commander, Colonel Frank Jenkins: yes, at least two men, maybe more; no, he didn't see their faces, they were wearing helmets and masks, etc. 

When he finally catches up with Maria she is sitting on the sofa in his office with the phone pressed to her ear. She's taken off her earring as is her habit, and is rubbing the enormous pearl between her fingers. "—oh yes, darling, would you? Peg, I would be so immensely grateful," and right, that's a good idea, calling Peggy. He was going to do it himself, right after he talked to their pilot and tells him he wants to delay their flight to the Bahamas by an hour or so. 

He expects Maria to tell him to pick up the call at the desk, but instead she just puts the phone back into its cradle. "Did you tell her what happened?" Howard asks. 

"Yes," Maria says. 

"What did she say?" Howard asks. 

"She's sending a car," Maria says. 

Howard frowns. "A car? Why? We'll still make it—we'll have dinner on the plane and be at the house in time for a nightcap." 

Maria stands up. "I'm not going to the house. I'm going to stay with Peggy for a while. I'll have Jarvis bring over my things," and Howard looks down at the top of his desk, stares at the pile of papers, the solid gold paperweight, the framed pictures of Tony aged three and Steve Rogers aged twenty-six, and waits for the words—impossible words, and at the same time, inevitable. 

"Howard, I want a divorce," Maria says, and _right, yeah, there we go._

His mind goes strangely blank, but he's saved from having to reply by the return of Colonel Jenkins, who reports that they've captured one of the assailants—can he come right away? "Sure," Howard replies, and Maria snorts softly and turns away as he follows Jenkins out and down to where a black-clad figure is being held by no fewer than four armed guards. 

They pull off his goggles and mask to reveal a sullen, sneering face. "Do you recognize this man?" Jenkins asks Howard. 

Howard studies him closely, then shakes his head. "I've never seen this guy before in my life." 

  
  


###  1945 

"I gotta put her in the water." Steve turns toward him, face contorted, agonized. 

Bucky feels like his chest is collapsing, _he can't breathe, he can't breathe._ "I—Okay. _Okay."_

Steve grits out, "There's not gonna be time otherwise. It's heading for New York." 

"Right. Yeah. So do it," Bucky manages. "You _gotta."_

Steve's face convulses: tears stream down his face and then, just as suddenly, stop. "I'm sorry. Buck, I'm so— " and Bucky goes to him, then, and kisses his wet, salty cheek, then his mouth. This is new, it's so new between them, how can it can already be over? It can't be over. Steve's hands are still on the plane's controls, and Bucky puts his own hands over them, and squeezes. 

"It's all right. I don't know how, but somehow it's gonna be all right. You wait and see," and then together they push, hard, on the throttle, and hold each other close as the plane goes down. 

  
  


###  1944 

Bucky slips away from the pub early. He's lost his taste for alcohol, and so has Steve, he thinks, but Steve feels obligated to show camaraderie with the other guys. Bucky feels no such compunction—not when he can sleep in a real bed without getting shot. Tomorrow he won't have that chance; they'll be back on mission tomorrow. But tonight he's got a bunk in the safest place in the world, the SSR base in London—and hell, _Winston Churchill_ is down here somewhere. 

His room is at the end of a narrow hall three stories underground. It feels like the corridor of a submarine, lit by only a single, flickering bulb in a wire cage. There's someone down near his door, and Bucky's had a good meal and two beers and he's tired, so his sense of danger doesn't kick in until he gets close enough to see that—it's Steve. Which is impossible, because he's just left Steve, and his hand goes to his gun, his gun's in his hand: raised, cocked, aimed. 

Steve raises both palms and stares grimly at him. Steve doesn't say anything, just waits, and that's what abruptly convinces Bucky that this really _is_ Steve, because he recognizes Steve's stubborn patience. When the going gets tough, Steve grits his teeth and waits it out, and right now Steve's waiting _him_ out, waiting for Bucky to recognize him even though he's—different, again. Changed, again. This Steve's got lines on his face and looks older and more battleworn—an effect of the serum? Or has there been some other goddamned experiment? Bucky thinks of the labs downstairs, of Howard Stark working like a squirrel— and stifles a bitter laugh, because he was wrong, wasn't he, to think of the SSR as _a safe place._ It's not. 

Bucky lowers the gun and says, sighing, "What happened to you?" and when Steve laughs, quick and brittle, Bucky nearly raises the gun again—because his Steve doesn't laugh like that. 

"A lot," this Steve says. "A _lot,"_ and then, "But that's not...I need to talk to you, Buck. Can we...?" Steve jerks his head at the door, and Bucky nods and unlocks it. The room is tiny, barely enough for the bed and his trunk and a chair, but it's better than the barracks: no stinky guys snoring or playing cards or playing with themselves. Bucky offers Steve the chair, but when the door closes, Steve's reaches for his neck like he couldn't do when he was small, and Bucky turns into the hug and makes tight fists in the back of Steve's jacket. This is not gonna be good news, he knows that already, but that's all the more reason to give Steve this moment of consolation, and to take a little bit of that consolation for himself. 

Bucky presses his face— eyes, cheek, nose—against the warm, faintly spicy skin of Steve's neck, and then jerks up. "Okay, pal, spill. Am I gonna die? Are _you_ gonna die? What gives?" 

Whatever it is makes Steve go pale. "No. _Neither,"_ Steve says hollowly. "It's _worse,"_ and damn if that doesn't send a chill up Bucky's spine, because Steve's no chickenshit when it comes to suffering. Steve understands illness; Steve and pain are old friends. Steve's not scared of dying—hell, he's not scared of _much._

_"What_ then?" Bucky asks, pretty sure he doesn't want to know. 

"Nothing,"' Steve says, tight-lipped. "Just. Don't go on the mission tomorrow, all right? That's the beginning, middle and end of what I've come here to tell you. Don't go, Buck." 

_"Don't go?"_ Bucky repeats. "You know, it ain't exactly _optional."_

"Tell them you're sick. You've never in your life refused a mission, they'll believe you. Tell _me,_ I'll believe you," Steve says thickly, and holy fuck, are those tears welling up in his eyes? Bucky stares—reaches out for him—because Steve's no chickenshit when it comes to suffering —and is shocked when Steve grabs him and yanks their mouths together and _kisses him._ Bucky likes to think of himself as a cool customer, as someone who thinks fast on his feet and is ready for anything. But _this_ he's not ready for, _this_ he isn't prepared for—because it's never been worth wondering what the hell he would do if this happened because _it wasn't ever gonna happen._

Except now it has, and Steve is kissing the breath out of him, tongue in his mouth and arms tight around him, and fuck, Bucky's hard, he wants this, but this is crazy, they don't do this—and that's the thought that lets him struggle back to sense and shove Steve back and away. 

"I don't know where you come from, but—we don't _do_ this, you and me. We've never—" 

"I know, 'cause we're _fools,"_ Steve says, almost savagely. "But it's different in the future, it's all different—or it can be. You just have to stay off that goddamned train, Buck: you'll know the one. Remind me of that day we rode the Cyclone together. Tell me you feel just like I did, but worse. Tell me any damn thing you want but just stay back on that mountain. Swear to me; swear it." 

Bucky hesitates, but it's never a question really. He's always followed Steve's lead; it's the one thing he knows how to do, the one thing he has faith in. "Yeah, all right, Steve," he says. "I swear to God, I swear to you, whatever you want," and Steve's shoulders drop as he relaxes. 

**Author's Note:**

> Enormous thanks to lim and to Monica for beta! Merry and I brainstormed this story post-Endgame because the Science Bros are a little trickier than some pairings to write in the aftermath, so I got invested in figuring out ways to do it. This was one, and then we both got interested in thinking about a world without Tony Stark as he was in canon. And we realized that Bucky/The Winter Soldier had a real effect on who Tony became. And that Steve has a goddamned time machine which is very very dangerous. Anyway we wrote this together to figure it all out - next time humanity will survive, promise!
> 
> And if you liked it, please consider [reblogging on tumblr](https://cesperanza.tumblr.com/post/186048633995/this-has-already-happened-mollyamory-molly).


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